Guessing whether people will unsubscribe from your mailing lists
Suppose that you have an administrative mailing list (or mailing lists), you understand that people can always unsubscribe one way or another, and you want to have some idea if people are going to do so. Here is my modest suggestion on a simple question to ask yourself about the messages going to the mailing list: are the mailing list messages actionable?
(Alternately you've been forced to run some mailing lists that people can't officially unsubscribe from and you'd like some guess at how many people actually read the messages.)
'Actionable' is jargon, but it's useful jargon. An actionable message is one that causes people to do things. So, does your average message tell the average recipient about something that the recipient needs to do (or know) right now or very soon? If they do not, some recipients may find the messages interesting but I think that a lot of people won't and are going to drop them.
(But, you say, your messages are full of interesting things. That's nice, but look, would your 'interesting things' go even moderately viral on Facebook or Twitter or wherever, even among a limited audience? If the answer is 'of course not' then they are nowhere near as interesting as you think. Being genuinely interesting is a very, very high bar.)
Obviously, the more actionable to the more people the better off you are and the less actionable you are to fewer and fewer people, well, that's not good. Completely non-actionable cheerful messages from eg your Dean (or some other high manager of your choice) almost certainly go straight to the round file.
(The unfortunate but honest truth is that today we simply don't have a good communication system for these sort of newsletter type things, at least if they're supposed to be relatively private. Email has stopped being it for all sorts of reasons that I don't feel like trying to write down in this entry.)